Transmitter Receiver Leakage Reduction In A Full Duplex System Without The Use Of A Duplexer

ABSTRACT

A transceiver suitable for frequency duplex division communication is disclosed. The transceiver comprises a transmitter, wherein the transmitter comprises a power amplifier; a receiver; an auxiliary power amplifier which is arranged to provide a controllable phase shift and gain output; a first filter arranged at an output of the power amplifier arranged to attenuate frequencies at a receiving frequency of the receiver; a second filter arrangement at an output of the auxiliary power amplifier arranged to attenuate frequencies at a receiving frequency of the receiver; and a signal transmission arrangement. The signal transmission arrangement is arranged to transmit signals provided from the transmitter through its power amplifier to a radio frequency, RF, connecting point, receive signals from the RF connecting point and provide the signals to the receiver, and provide signals from the auxiliary amplifier towards an input of the receiver. The transceiver also comprises a controller, wherein the controller is arranged to control the auxiliary power amplifier output to provide a signal that has a phase and amplitude in relation to the output of the power amplifier of the transmitter such that the transmitter contribution to the signal at the input of the receiver is suppressed. A method of controlling the transceiver, a communication device and computer program are also disclosed.

TECHNICAL FIELD

The present invention generally relates to a transceiver, a method ofoperating the transceiver, and a computer program for implementing themethod. The present invention also relates to a communication devicecapable of frequency division duplex communication comprising such atransceiver.

BACKGROUND

Transceivers comprise both a transmitter and a receiver, and arecommonly used in a variety of communication apparatuses. Transceiverscan be arranged to be operated in semi-duplex, i.e. the receiver andtransmitter operates on same frequency but separated in time to preventthe transmitter signal from concealing the received signal. Thisapproach is therefore commonly referred to as time division duplex(TDD). Transceivers can also be operated in full duplex, i.e. thereceiver and transmitter operates simultaneously wherein some specialarrangements are provided to prevent the transmitter from concealing thereceived signal. One approach to achieve this is to assign differentfrequencies for transmission and reception. This approach is thereforecommonly referred to as frequency division duplex (FDD).

Often the receiver and the transmitter use the same antenna, or antennasystem which may comprise several antennas, which implies that some kindof circuitry may be desired to enable proper interaction with theantenna. This circuitry should be made with certain care when operatingthe transceiver in full duplex since the transmitter signal, althoughusing FDD may interfere with the received signal. FIG. 1 illustrates anexample of a communication apparatus 100 comprising a transceiver 102,an antenna 104 connected to the transceiver 102, and further circuitry106 such as processing means, input and output circuitry, and memorymeans. The transceiver 102 comprises a transmitter 108, a receiver 110,and a duplexer 112 which is connected to the transmitter 102, thereceiver 110 and the antenna 104. The duplexer 112 is arranged to directradio frequency (RF) energy from the transmitter to the antenna, asindicated by arrow 114, and from the antenna to the receiver, asindicated by arrow 116, and can for example comprise a circulator.Duplexers are known in the art and for example described in U.S. Pat.No. 4,325,140. However, duplexers are not ideal and a leakage oftransmitter signals from the transmitter to the receiver, as indicatedby arrow 118, is at least to some degree present. Further, duplexers arecommonly costly, space consuming and unable to be implemented on-chip.Therefore, efforts have been made in the art to achieve the similareffects with on-chip solutions. These are based on electrical balance byusing a dummy load which is arranged to be equal to the antennaimpedance. Thus, a first portion of energy is directed towards theantenna for transmission, and a second portion of the energy is directedtowards the dummy load where it is dissipated as heat. If the dummy loadis configured to have an impedance equal to that of the antenna, thefirst and second portions are equal, and, when using a differentialinput to the receiver, the contribution at receiver input from thetransmitted signal can be suppressed. An example of such approach isdisclosed in US 2011/0064004 A1. However, here it can be seen that halfof the transmission energy is lost in heat dissipation in the dummyload.

It is therefore a desire to provide an approach for transceivers wherethe above discussed drawbacks are reduced.

SUMMARY

An object of the invention is to at least alleviate the above statedproblem. The present invention is based on the understanding that byproviding a counter-contribution to the contribution of a poweramplifier of a transmitter at the input of a receiver in a transceiverarrangement, the contribution can be suppressed. An auxiliary poweramplifier provides the transmit signal with a certain amplitude andphase shift for providing this counter-contribution. Thecounter-contribution can be applied in different ways, as will bedemonstrated below. To further decrease impact by the output of thepower amplifier at receiving frequencies at the input of the receiver,and also such impact by the auxiliary power amplifier, filtering of theoutputs of the power amplifier and the auxiliary power amplifier isprovided, thereby reducing transmitter noise at the input of thereceiver.

According to a first aspect, there is provided a transceiver suitable tofrequency duplex division communication. The transceiver comprises atransmitter, wherein the transmitter comprises a power amplifier; areceiver; an auxiliary power amplifier which is arranged to provide acontrollable phase shift and gain output; a first filter arranged at anoutput of the power amplifier arranged to attenuate frequencies at areceiving frequency of the receiver; a second filter arrangement at anoutput of the auxiliary power amplifier arranged to attenuatefrequencies at a receiving frequency of the receiver; and a signaltransmission arrangement. The signal transmission arrangement isarranged to transmit signals provided from the transmitter through itspower amplifier to a radio frequency, RF, connecting point, receivesignals from the RF connecting point and provide the signals to thereceiver, and provide signals from the auxiliary amplifier towards aninput of the receiver. The transceiver also comprises a controller,wherein the controller is arranged to control the auxiliary poweramplifier output to provide a signal that has a phase and amplitude inrelation to the output of the power amplifier of the transmitter suchthat the transmitter contribution to the signal at the input of thereceiver is suppressed.

The receiving frequency of the receiver may be lower than a transmittingfrequency of the transmitter, wherein the first filter may be ahigh-pass filter or a band-pass filter, and the second filter may be ahigh-pass filter or a band-pass filter. The band-pass filters of thefirst and second filters may each comprise a first capacitance and aninductance coupled in parallel where the parallel coupling is coupled inseries with a second inductance. According to one option, at least oneof the capacitance and the first and second inductances of each of thefirst and second filters may be controllable and may then be controlledby the controller.

The receiving frequency of the receiver may be higher than atransmitting frequency of the transmitter, wherein the first filter maybe a low-pass filter or a band-pass filter, and the second filter may bea low-pass filter or a band-pass filter. The band-pass filters of thefirst and second filters may each comprise a capacitance and a firstinductance coupled in parallel, where the parallel coupling is coupledin series with a second capacitance. According to one option, at leastone of the inductance and the first and second capacitances of each ofthe first and second filters may be controllable and may then becontrolled by the controller.

The controller may be arranged to control an input to the auxiliarypower amplifier such that the auxiliary power amplifier is enabled toprovide the controllable phase shift and gain output. The control of theinput to the auxiliary power amplifier may be a control of a basebandcircuit connected to the transceiver.

The controller may be arranged to control the auxiliary power amplifiersuch that the auxiliary power amplifier is enabled to provide thecontrollable phase shift and gain output.

The signal transmission arrangement may comprise a first impedanceelement connected between an output of the auxiliary power amplifierfilter and an input of the receiver; and a second impedance elementconnected between an output of the power amplifier filter of thetransmitter and the input of the receiver wherein the second impedanceelement also is connected between the RF connecting point and the inputof the receiver. The first impedance element may have controllableimpedance, the second impedance element may have controllable impedance,and the controller may be arranged to control also impedances of thefirst impedance element and the second impedance element. The output ofthe auxiliary power amplifier may be controlled to have a relation inphase to the output of the power amplifier of the transmitter and tohave an amplitude having a relation to the output of the power amplifierof the transmitter, and the first and second impedance elements may becontrolled to have a corresponding relation of their impedances. Theoutput of the auxiliary power amplifier may be controlled to haveopposite phase to the output of the power amplifier of the transmitterand to have equal amplitude to the output of the power amplifier of thetransmitter, and the first and second impedance elements have equalimpedances.

The second impedance element may comprise a first and a second impedanceconnected in series, and the controller may be arranged to provide itscontrol by a feedback structure and measure at a point between the firstand second impedances of the second impedance element and the output ofthe auxiliary power amplifier wherein feedback is based on themeasurements.

The transceiver may further comprise a parallel resonance tank circuitincluding the first and second impedance elements and a third impedanceelement connected between the output of the auxiliary power amplifierfilter and the power amplifier filter of the transmitter, wherein theparallel resonance tank is tuned to a frequency of a signal componentreceived by the signal transmission arrangement that is desired to besuppressed.

The receiver may further comprise a receiver impedance element at theinput of the receiver, the receiver impedance element may havecontrollable impedance, and the controller may be arranged to controlthe receiver impedance element such that the second impedance elementand the receiver impedance element together have a resonance frequencyequal to a frequency of a signal desired to be received by the receiver.

The first and second impedance elements may comprise inductors. Thefirst and second impedance elements may comprise capacitors.

The signal transmission arrangement may comprise a connection couplingthe output signal from the first filter to the RF connecting point; aprimary winding coupling a signal from the RF connecting point to thereceiver via a capacitance; and a secondary winding interacting with theprimary winding and coupled to the output of the second filter of theauxiliary power amplifier such that the provision of the signals fromthe auxiliary power amplifier is enabled.

The signal transmission arrangement may comprise a primary windingconnected to the RF connecting point and a secondary winding interactingwith the primary winding, wherein the secondary winding is coupling asignal from the RF connecting point to the receiver, and wherein theprimary winding is coupled to the output of the second filter of theauxiliary power amplifier such that the provision of the signals fromthe auxiliary power amplifier is enabled, and to a third filterconnected to a reference voltage such that current swing at thereceiving frequency is enabled in the primary winding.

The signal transmission arrangement may comprise a primary windingconnected to the RF connecting point and a secondary winding interactingwith the primary winding, wherein the secondary winding is coupling asignal from the RF connecting point to the receiver, and wherein theprimary winding is coupled to a third filter connected to a referencevoltage such that current swing at the receiving frequency is enabled inthe primary winding, the third filter comprising a further primarywinding, wherein a further secondary winding interacting with thefurther primary winding which is coupled to the output of the secondfilter of the auxiliary power amplifier such that the provision of thesignals from the auxiliary power amplifier is enabled.

The signal transmission arrangement may comprise a first primary windingconnected to the RF connecting point, a second primary winding, andsecondary winding interacting with the first and secondary primarywindings, wherein the secondary winding is coupling a signal from the RFconnecting point to the receiver, and wherein the first primary windingis coupled to a third filter connected to a reference voltage such thatcurrent swing at the receiving frequency is enabled in the first primarywinding, and the second primary winding is coupled to the output of thesecond filter of the auxiliary power amplifier such that the provisionof the signals from the auxiliary power amplifier is enabled.

The signal transmission arrangement may comprise a connection couplingthe output signal from the first filter to the RF connecting point; anda third filter coupling a signal from the RF connecting point to thereceiver, wherein the output of the second filter is connected directlyto the input of the receiver.

The receiving frequency of the receiver may be lower than a transmittingfrequency of the transmitter, and the third filter may then be alow-pass filter or a band-pass filter. The band-pass filter of thirdfilter may comprise a capacitance and a first inductance coupled inparallel, where the parallel coupling is coupled in series with a secondcapacitance. According to one option, at least one of the inductance andthe first and second capacitances of the third filter may becontrollable and may then be controlled by the controller.

The receiving frequency of the receiver may be higher than atransmitting frequency of the transmitter, and the third filter may thenbe a high-pass filter or a band-pass filter. The band-pass filter ofthird filter may comprise a first capacitance and an inductance coupledin parallel, with the parallel coupling coupled in series with a secondinductance. According to one option, at least one of the capacitance andthe first and second inductances of the third filter may be controllableand may then be controlled by the controller.

The controller may be arranged to provide its control by a feedbackstructure and measure the output of the power amplifier of thetransmitter and the output of the auxiliary power amplifier whereinfeedback is based on the measurements.

The controller may be arranged to provide its control by a feedbackstructure and measure the transmitter contribution at the input of thereceiver wherein feedback is based on the measurement.

According to a second aspect, there is provided a communication device,capable of frequency division duplex communication in a communicationnetwork, comprising a transceiver according to the first aspect.

According to a third aspect, there is provided a method for controllinga transceiver. The transceiver comprises a transmitter comprising apower amplifier, a receiver, an auxiliary power amplifier which hascontrollable phase shift and gain output, a first filter arranged at anoutput of the power amplifier arranged to attenuate frequencies at areceiving frequency of the receiver, a second filter arrangement at anoutput of the auxiliary power amplifier arranged to attenuatefrequencies at a receiving frequency of the receiver, a signaltransmission arrangement arranged to transmit signals provided from thetransmitter through its power amplifier to a radio frequency, RF,connecting point, receive signals from the RF connecting point andprovide the signals to the receiver, and provide signals from theauxiliary amplifier towards an input of the receiver. The methodcomprises controlling an output of the auxiliary power amplifier toprovide a signal that has a phase and amplitude in relation to theoutput of the power amplifier of the transmitter such that thetransmitter contribution to the signal at the input of the receiver issuppressed.

Where the signal transmission arrangement comprises a first impedanceelement connected between an output of the auxiliary power amplifierfilter and an input of the receiver, and a second impedance elementconnected between an output of the power amplifier filter of thetransmitter and the input of the receiver wherein the second impedanceelement also is connected between the RF connecting point and the inputof the receiver, wherein the first impedance element has controllableimpedance and the second impedance element has controllable impedance,the method may further comprise controlling the impedances of the firstand second impedance elements.

The controlling may further comprise controlling the output at theauxiliary power amplifier to have a relation in phase to the output ofthe power amplifier of the transmitter and to have an amplitude having arelation to the output of the power amplifier of the transmitter, andthe first and second impedance elements to have a corresponding relationof their impedances.

The controlling further comprise controlling the output at the auxiliarypower amplifier to have opposite phase to the output of the poweramplifier of the transmitter and to have equal amplitude to the outputof the power amplifier of the transmitter, and the first and secondimpedance elements have equal impedances.

Where the signal transmission arrangement comprises a connectioncoupling the output signal from the first filter to the RF connectingpoint, a primary winding coupling a signal from the RF connecting pointto the receiver via a controllable capacitance such that receivedsignals are provided to the receiver, and a secondary windinginteracting with the primary winding and coupled to the output of thesecond filter of the auxiliary power amplifier such that the provisionof the signals from the auxiliary power amplifier is enabled, the methodmay further comprise controlling the controllable capacitance.

Where the signal transmission arrangement comprises a primary windingconnected to the RF connecting point and a secondary winding interactingwith the primary winding, wherein the secondary winding is coupling asignal from the RF connecting point to the receiver, and wherein theprimary winding is coupled to the output of the second filter of theauxiliary power amplifier such that the provision of the signals fromthe auxiliary power amplifier is enabled, and to a third filterconnected to a reference voltage such that current swing at thereceiving frequency is enabled in the primary winding, the method mayfurther comprise controlling the third filter.

Where the signal transmission arrangement comprises a primary windingconnected to the RF connecting point and a secondary winding interactingwith the primary winding, wherein the secondary winding is coupling asignal from the RF connecting point to the receiver, and wherein theprimary winding is coupled to a third filter connected to a referencevoltage such that current swing at the receiving frequency is enabled inthe primary winding, the third filter comprising a further primarywinding, wherein a further secondary winding interacting with thefurther primary winding which is coupled to the output of the secondfilter of the auxiliary power amplifier such that the provision of thesignals from the auxiliary power amplifier is enabled, the method mayfurther comprise controlling the third filter.

Where the signal transmission arrangement comprises a first primarywinding connected to the RF connecting point, a second primary winding,and secondary winding interacting with the first and secondary primarywindings, wherein the secondary winding is coupling a signal from the RFconnecting point to the receiver, and wherein the first primary windingis coupled to a third filter connected to a reference voltage such thatcurrent swing at the receiving frequency is enabled in the first primarywinding, and the second primary winding is coupled to the output of thesecond filter of the auxiliary power amplifier such that the provisionof the signals from the auxiliary power amplifier is enabled, the methodmay further comprise controlling the third filter.

Where the signal transmission arrangement comprises a connectioncoupling the output signal from the first filter to the RF connectingpoint, and a third filter coupling a signal from the RF connecting pointto the receiver, wherein the output of the second filter is connecteddirectly to the input of the receiver, the method may further comprisecontrolling the third filter. The receiving frequency of the receivermay be lower than a transmitting frequency of the transmitter, and thethird filter may be a band-pass filter, wherein the band-pass filter ofthird filter comprises a capacitance and a first inductance coupled inparallel, where the parallel coupling is coupled in series with a secondcapacitance and at least one of the inductance and the first and secondcapacitances of the third filter is controllable, wherein thecontrolling of the third filter may comprise controlling at least one ofthe inductance and the first and second capacitances of the thirdfilter. The receiving frequency of the receiver may be higher than atransmitting frequency of the transmitter, and the third filter is aband-pass filter, wherein the band-pass filter of third filter maycomprise a first capacitance and an inductance coupled in parallel, withthe parallel coupling coupled in series with a second inductance,wherein at least one of the capacitance and the first and secondinductances of the third filter is controllable, wherein the controllingof the third filter may comprise controlling at least one of thecapacitance and the first and second inductances of the third filter.

The controlling may be feedback controlling by measuring the output ofthe power amplifier of the transmitter and the output of the auxiliarypower amplifier wherein the feedback controlling is based on themeasurements.

The controlling may be feedback controlling by measuring the transmittercontribution at the input of the receiver wherein the feedbackcontrolling is based on the measurement.

The receiver may further comprise a receiver impedance element at theinput of the receiver, the receiver impedance element has controllableimpedance, wherein the method further may comprise controlling theimpedance of the receiver impedance element such that a path from the RFconnecting point towards the receiver of the signal transmissionarrangement and the receiver impedance element together have a resonancefrequency equal to a frequency of a signal desired to be received by thereceiver.

The controlling of the output of the auxiliary power amplifier maycomprise controlling an input signal to the auxiliary power amplifier.The controlling of the input signal to the auxiliary power amplifier maycomprise controlling a baseband circuit connected to the transceiver.

The controlling of the output of the auxiliary power amplifier maycomprise controlling the auxiliary power amplifier such that theauxiliary power amplifier is enabled to provide the controllable phaseshift and gain output.

According to a fourth aspect, there is provided a computer programcomprising computer executable instructions which when executed by aprogrammable controller of a transceiver causes the controller toperform the method according to the third aspect.

Other objectives, features and advantages of the present invention willappear from the following detailed disclosure, from the attacheddependent claims as well as from the drawings. Generally, all terms usedin the claims are to be interpreted according to their ordinary meaningin the technical field, unless explicitly defined otherwise herein. Allreferences to “a/an/the [element, device, component, means, step, etc]”are to be interpreted openly as referring to at least one instance ofsaid element, device, component, means, step, etc., unless explicitlystated otherwise. The steps of any method disclosed herein do not haveto be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of thepresent invention, will be better understood through the followingillustrative and non-limiting detailed description of preferredembodiments of the present invention, with reference to the appendeddrawings.

FIG. 1 is a block diagram which schematically illustrates a conventionalcommunication apparatus comprising a transceiver.

FIG. 2 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 3 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 4 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 5 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 6 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 7 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 8 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 9 is a block diagram which schematically illustrates transceiveraccording to an embodiment.

FIG. 10 illustrates a filter according to an embodiment.

FIG. 11 illustrates a filter according to an embodiment.

FIG. 12 is a flow chart which schematically illustrates a methodaccording to embodiments.

FIG. 13 schematically illustrates a computer program and a processor.

FIG. 14 is a block diagram schematically illustrating a communicationdevice according to an embodiment.

FIG. 15 is a block diagram schematically illustrating a transceiveraccording to an embodiment.

FIG. 16 is a block diagram schematically illustrating a transceiveraccording to an embodiment.

FIG. 17 is a block diagram schematically illustrating a transceiveraccording to an embodiment.

DETAILED DESCRIPTION

FIG. 2 is a block diagram which schematically illustrates a transceiver200 according to an embodiment. The transceiver 200 comprises atransmitter 202, a receiver 204, and a signal transmission arrangement206, such as the depicted antenna arrangement, or a wired connection.The transmitter 202 comprises a power amplifier (PA) 208, and can alsocomprise further transmitter circuitry 210, which further transmittercircuitry however is not further discussed in this disclosure since itdoes not have impact of the inventive contribution to the art. Theantenna arrangement 206 is arranged to transmit radio frequency signalsprovided from the transmitter 202 through its power amplifier 208, andis also arranged to receive radio frequency signals and provide them tothe receiver 204. The transceiver 200 further comprises an auxiliarypower amplifier 212 which has controllable phase shift and gain. Thefunction of the auxiliary PA 212 will be discussed below. Thetransceiver 200 also comprises a first impedance element 214 and asecond impedance element 216 which have controllable impedances. Thefunction of the first and second impedance elements 214, 216 will bediscussed below. The auxiliary PA 212 has its input connected to eitherthe input of the PA 208 of the transmitter 202 or connected to beprovided with an adjusted input as will be further elucidated below, andits output connected to a filter 213 which is arranged to let throughfrequencies at which the transceiver 200 is transmitting whileattenuating at frequencies at which the transceiver 200 is receiving.Thereby, noise that may be caused by the auxiliary PA at the receivingfrequencies will be attenuated before reaching the input of thereceiver. The output of the filter 213 is connected to the firstimpedance element 214, which is connected between the output filter 213of the auxiliary PA and an input of the receiver 204. The secondimpedance element 216 is connected between an output of a correspondingfilter 209 of the PA 208 of the transmitter 202 and the input of thereceiver 204, i.e. the first and second impedance elements 214, 216 areconnected in series between the output of the filter 213 of theauxiliary PA 212 and the output of the filter 209 of the PA 208 of thetransmitter 202 as a voltage divider there between, wherein the dividedvoltage is provided to the input of the receiver 204. This structurewill be used for the function demonstrated below for this embodiment.The transceiver 200 also comprises a controller 218 which is arranged tocontrol the auxiliary PA 212, and optionally also to control the firstimpedance element 214 and the second impedance element 216.

The output of the auxiliary PA 212, i.e. phase and amplitude, can becontrolled by controlling the auxiliary PA 212 itself, as indicated inFIG. 15, wherein the auxiliary PA 212 can have the same signals as inputas the PA 208. Alternatively, the input to the auxiliary PA 212 isadjusted either by a separate adjustment element, as indicated in FIG.16, adjusting the input to the auxiliary PA 212 such that the output ofthe auxiliary PA 212 gets the properties as elucidated below, or by abaseband circuit, as indicated in FIG. 17, connected to the transceiver200. The baseband circuit then provides an adjusted input to theauxiliary PA 212. In the latter example, the baseband circuit can forexample be a digital baseband circuit where the adjusted input to theauxiliary PA 212 is adjusted in digital domain.

By controlling the output of the auxiliary PA 212 to have a phase andamplitude, which when voltage division by the controlled first andsecond impedance elements 214, 216 between the voltages of the output ofthe auxiliary PA 212 and the output of the PA 208 of the transmitter202, the divided voltage can be such that the transmitter contributionto the signal at the input of the receiver is reduced. One example isthat the auxiliary PA 212 outputs the same voltage as the PA 208, butwith opposite phase, and the first and second impedance elements arecontrolled to have mutually equal impedances. Here, “opposite phase”should be construed in its technical context where exactly a 180 degreephase shift may not be the optimised value, as for one example where thebest suppression was found to be reached somewhere between 172 and 173degrees in that particular case. Due to imperfections, the optimisedvalue may not be reached, at least not at all times, in a real-worldimplementation, and the ideal situation with total cancelling is inpractical implementations not reachable. In an ideal (but fictive)situation, the contribution from the transmitter at the receiver inputwould however be zero. The ratio between the output of the auxiliary PA212 and the output of the PA, and corresponding ratio between the firstand second impedance elements 214, 216 can be chosen in different ways.Here it should be noted that the second impedance element 216 will alsobe a part of the reception path from the antenna arrangement 206 to thereceiver 204. Thus, the control mechanism can set a restriction for thesecond impedance element 216 based on receiver properties, and thecontrol is then made on the auxiliary PA 212 and the first impedanceelement 214 to achieve the reduction of transmitter contribution to thereceiver input. The structure provides for a multitude of controlstrategies, and a selection thereof will be demonstrated below.

Thus, the controller 218 can be arranged to control both the output ofthe auxiliary PA 212, to provide a signal that has a phase and amplitudein relation to the output of the PA 208 of the transmitter 202, and thefirst and second impedance elements 214, 216 such that the transmittercontribution to the signal at the input of the receiver is reduced. Thereader may at this point ask why the parameters are not set to the rightvalues, and the transceiver will work properly. However, the impedanceof the signal transmission arrangement can change substantially duringoperation, for example due to the changing environment of an antenna ina handheld device when held in different ways, and due to operation indifferent frequency bands. But upon considering a particular use casefor a transceiver where such phenomena are not present, the controller212 can be omitted, and the structure demonstrated above can be usedwith fixed parameters. Thus, the controller is not essential for theoperation in all situations, or can be considered to be a fixedparameter setting for the particular transceiver implementation.

The receiver 204 can optionally further comprise, in addition to otherreceiver circuitry 220, which further receiver circuitry however is notfurther discussed in this disclosure since it does not have impact ofthe inventive contribution to the art, a receiver impedance element 221at the input of the receiver 204. The receiver impedance element 221 hascontrollable impedance, and the controller 218 is arranged to controlthe receiver impedance element such that the second impedance element216 and the receiver impedance element 221 together have a resonancefrequency equal to a frequency of a signal desired to be received by thereceiver 204. This provides for a further degree of freedom incontrolling the transceiver.

The output filters 209, 213 of the PA and auxiliary PA are arranged topass frequencies at which transmitting is performed and attenuatingfrequencies at which receiving is performed by the transceiver 200. Thisis suitable when frequency division duplex (FDD) is employed, i.e. wheretransmit and receive frequencies are structurally separated. Thefiltering can be arranged in different ways, such as for examplenotching at frequencies of receiving by the transceiver 200. Thetransceiver 200 when operating in a communication system employing FDDcan however, due to allocation of receive and transmit frequencies inthe particular system, use low-pass or high-pass filters since it thenis given that the receive frequency is higher or lower than the transmitfrequency. This implies that filter design can be easier and/or moreefficient filters can be used. For example, if it is known that thereceive frequency is always lower, e.g. by a certain distance infrequency, than the transmit frequency, then high-pass filters can beused for the output filters 209, 213 of the PA 208 and the auxiliary PA212. For the opposite case, i.e. receive frequency is always higher thantransmit frequency, low-pass filters can be used. The filters can becontrolled, i.e. their frequency properties such as cut-off frequency,such that change of operation frequency of the transceiver 200 can behandled. The implementation of the high-pass and low-pass filters can bemade quite simple but may then not provide high enough attenuation atreceive frequencies and/or cause too much loss in transmit frequencies,particularly when receive and transmit frequencies are fairly close infrequency. It has been found beneficiary to use a band-pass filter, forexample as demonstrated with reference to FIGS. 10 and 11 below, toachieve good attenuation at receive frequencies and low loss at transmitfrequencies. This is particularly beneficiary in the situationdemonstrated above.

FIG. 3 is a block diagram which schematically illustrates a transceiver300 according to an embodiment. In FIG. 3, a number of alternatives formeasuring a signal which is significant for the transmitter contributionto the receiver input are illustrated, and will be discussed below. Bymeasuring such significant signal or signals, a feedback structure ofthe controller can be provided to adaptively control parameters of thecontrollable elements of the structure. The structure is similar to thatillustrated in FIG. 2 except that the second impedance element of FIG. 2is here substituted by a second impedance element 316 which comprises afirst and a second impedance 315, 317 connected in series. This enablesa further option for the measurement of the significant signal. Theprinciple of measuring and controlling is however also applicable toother structures, such as those which will be demonstrated withreference to FIGS. 4 to 9, respectively. The principles of measuring thecontributions by the PA and the auxiliary PA, or measuring the actualcontribution at the input of the receiver, or a combination thereof, forcontrolling the auxiliary PA, and also different controllable impedancesand/or filters that are provided in the different structuresdemonstrated below, are however the same for all the embodiments.

Returning to FIG. 3, the measurements should be made such that themeasurement does not have impact on the radio signals in the receptionor transmit paths. By using high input impedance circuitry for themeasurements, this can be achieved. For the measurement points indicatedas “Alternative 1”, the signals at the outputs of the auxiliary PA andthe PA, or the outputs of the respective filters thereof, of thetransmitter are monitored, and based on these signals, the controller isable to perform the control according to the principles discussed above,i.e. to control the phase of the auxiliary PA and control the voltageand/or the impedances of the impedance elements such that the voltagedivision provides a reduced contribution from the transmitter to thereceiver input. Alternatively, the contribution from the transmitter ismeasured directly at the input of the receiver, as indicated as“Alternative 2”. This alternative may also need information, e.g. bymeasuring for example at PA output of the transceiver, about thetransmit signal. Further alternatively, as indicated as “Alternative 3”,the measurement can be made from the voltage division of the impedances315, 317 of the second impedance element 316, wherein for example afixed relationship between the impedances 315, 317 are chosen as adesigned relationship between the output voltages of the auxiliary PAand the PA of the transmitter, and the control mechanism is enabled tobe made very simple.

The feedback mechanism of the controller is thus arranged to minimisethe contribution from the transmitter at the input of the receiver. Thefeedback mechanism will then comprise a model for the chosen alternativeof measuring, and together with a chosen model for controlling theauxiliary PA and the impedance elements, the controller will providecontrol signals and the contribution will be kept reduced althoughchanges in signal environment such as antenna impedance and usedfrequency band occur.

FIG. 4 is a block diagram which schematically illustrates a transceiver400 according to an embodiment. The transceiver 400 has a similarstructure as the one illustrated in FIG. 2, but where the first andsecond impedance elements is constituted by a first variable capacitor414 and a second variable capacitor 416, and the receiver impedanceelement is a variable inductor 421. Here, the embodiment illustrated inFIG. 3 with the second impedance element having a first and secondimpedance can be understood from the embodiment of FIG. 4 to have afirst and a second variable capacitor as the first and secondimpedances.

In FIG. 4, an optional inductor 423 is illustrated, which together withthe capacitors 414, 416 form a parallel resonance tank which can betuned to a frequency of a signal received at the antenna which isdesired to be reduced. This frequency can for example be a signal from awireless local access network node which otherwise would interfere withfor example a desired signal from a cellular communication system basestation. An additional effect of the optional inductor is that biasingof the PA and the auxiliary PA is facilitated.

FIG. 5 is a block diagram which schematically illustrates a transceiver500 according to an embodiment. In FIG. 5, depiction of some elementssuch as the controller and control paths have been omitted for the sakeof easier understanding, since these features essentially correspond towhat has been demonstrated for the embodiments above. As demonstratedfor the embodiments above, the transceiver 500 comprises a transmitter502 with an output filter 509, a receiver 504, an antenna 506, and anauxiliary PA 512 with an output filter 513. Instead, FIG. 5 intends todemonstrate an alternative way of decreasing the transmittercontribution where the alternative instead of relying on a voltagedivision over impedances as demonstrated above relies on counteractingmagnetic fields generated in a transformer 515 where a primary winding516 connects the antenna 506, and thus also the transmitter 502 to theinput of the receiver 504. The magnetic field caused by the primarywinding 516 is thereby caused by these two components. A secondarywinding 514 is connected to the auxiliary PA, which by control ofamplitude and phase, as demonstrated above, is arranged to cause amagnetic field counteracting the magnetic field component caused by thetransmitter. The resulting magnetic field, which thereby will be theresulting signal towards the receiver, will thus only represent thesignal received by the antenna 506. Here, it should be noted that thefilter 513 due to its high impedance at receiving frequency makesreceiving signal drop over the transformer 515 negligible since thecurrent swing in the secondary winding 514 will be minimal. Noted shouldalso be that an impedance, here capacitor 521, can be connected betweenthe primary winding 516 and the input of the receiver 504 to provide alow-impedance path at receive frequency from the antenna 506. It shouldhere also be noted that the terms “primary” and “secondary” about thewindings are used only for distinguishing between them for clearerexplanation, and the opposite choice of terminology would be as correct,e.g. by considering the insertion of the counter-field by the auxiliaryPA to be at the “primary” winding.

FIG. 6 is a block diagram which schematically illustrates a transceiver600 according to an embodiment. In FIG. 6, depiction of some elementssuch as the controller and control paths have been omitted for the sakeof easier understanding, since these features essentially correspond towhat has been demonstrated for the embodiments above. As demonstratedfor the embodiments above, the transceiver 600 comprises a transmitter602 with an output filter 609, a receiver 604, an antenna 606, and anauxiliary PA 612 with an output filter 613. Here, a transformer 615comprises a primary winding 616 connected between the antenna 606, andthus the output of the filter 609 of the transmitter 602, and the outputof the filter 613 of the auxiliary PA 612. Already here, it can be seenthat by proper control of the auxiliary PA 612, the contribution fromthe transmitter 602 can be counter-acted. The transformer 615 alsocomprises a secondary winding 614 interacting with the primary winding616, wherein the secondary winding 614 is coupling a received signal tothe receiver 604. A filter 617 connected between a reference voltage andthe primary winding 616 provides for current swing at the receivingfrequency in the primary winding (the output filter 613 will not aselucidated with reference to FIG. 5). Thus, the filter 617 shouldprovide low impedance at receiving frequencies, and can also becontrollable by a controller to enable handling of different frequencyallocations. The received signal will thus be present across thesecondary winding 614 and can be coupled to the input of the receiver604, which here can have a differential low-noise amplifier withoutadditional balun.

FIG. 7 is a block diagram which schematically illustrates a transceiver700 according to an embodiment. The structure and principles of theembodiment shown in FIG. 7 resembles the one demonstrated with referenceto FIG. 6 with the difference that the signal from the auxiliary PA andits output filter is provided through a transformer 730 which is madepart of a filter 717 corresponding to the filter 617 of the embodimentof FIG. 6. The filter 717 comprises a capacitance 732 in parallel withan inductance 731 which is also a winding in the transformer 730. Thisparallel coupling is connected between a reference voltage and animpedance 734 which in turn is connected to a primary winding 716 of atransformer 715 which corresponds to the transformer 615 demonstratedwith reference to FIG. 6. Depending on the impedance 734, the filter 717will be a high-pass or a low-pass filter, which should be chosen to havelow impedance at receive frequencies and the selection of high-pass orlow-pass depends on frequency allocation for receive and transmitfrequencies, i.e. the impedance of the filter 717 should be high fortransmit frequencies. The contribution from the auxiliary PA is insertedby a secondary winding 729 (also here, the terms “primary” and“secondary” are just for distinguishing between the windings) which isconnected between the output of the filter of the auxiliary PA and areference voltage. In other senses, the features of this embodiment arethe same as for the one demonstrated with reference to FIG. 6.

FIG. 8 is a block diagram which schematically illustrates a transceiver800 according to an embodiment. The structure and principles of theembodiment shown in FIG. 8 resembles the one demonstrated with referenceto FIGS. 6 and 7 with the difference that the signal from the auxiliaryPA and its output filter is provided through a third winding 811 of atransformer 815, which otherwise corresponds to the transformers 615 and715 of FIGS. 6 and 7.

FIG. 9 is a block diagram which schematically illustrates a transceiver900 according to an embodiment. In FIG. 9, depiction of some elementssuch as the controller and control paths have been omitted for the sakeof easier understanding, since these features essentially correspond towhat has been demonstrated for the embodiments above. As demonstratedfor the embodiments above, the transceiver 900 comprises a transmitter902 with an output filter 909, a receiver 904, an antenna 906, and anauxiliary PA 912 with an output filter 913. The transmitter 902 isconnected via its output filter 909 to the antenna 906. The antenna 906is also connected to the input of the receiver 904 via a receiver filter921. Here, the transmitter filter 909 has low insertion loss at transmitfrequencies and high insertions loss at receive frequencies, while thereceiver filter 921 has low insertion loss at receive frequencies andhigh insertion loss at transmit frequencies. However, attenuation by thefilters 909, 921 is of course finite, wherein the auxiliary PA 912through its output filter 913 provides a countersignal directly at theinput of the receiver 904. The applied countersignal is controlled byadapting phase and amplitude, as for the other embodiments. In thisembodiment, the approach of measuring contribution at receiver input andproviding feedback control to the auxiliary PA provides for a fast anduncomplicated control mechanism.

The filters in the different embodiments demonstrated above can be mademore or less complex, and with different constraints on impedancematching. Simple filters comprising single capacitors or inductors maybe used, but may not fulfil the demands of constraints set up.High-order filters may on the other hand introduce other problems,and/or cost/space issues. FIG. 10 illustrates a filter 1000 according toan embodiment, which provides dual resonance properties where highinsertion loss is provided at one frequency and low insertion loss isprovided at another frequency not far from the first frequency, and hasbeen found a reasonable compromise for at least some of the embodiments.It comprises an inductance 1004 coupled in parallel with a capacitance1002, wherein the parallel coupling 1002, 1004 is coupled in series withan inductance 1006 between the input and output of the filter 1000. Itprovides a parallel resonance, attenuating the signal at a frequencybelow a series resonance where the signal is passed.

FIG. 11 illustrates a filter 1100 according to an embodiment, whichcorresponds to the filter demonstrated with reference to FIG. 10, butwith the difference that the parallel coupling 1102, 1104 is coupled inseries with a capacitance 1106 between the input and output of thefilter 1100, and that it provides a series resonance frequency below theparallel resonance frequency.

FIG. 12 is a flow chart which schematically illustrates a methodaccording to embodiments. The method is for controlling a transceiver asone of those demonstrated above. The method comprises filtering 1204 theoutput of the PA to attenuate frequencies at receiving frequencies, andfiltering 1206 the output of the auxiliary PA to attenuate frequenciesat receiving frequencies. The method comprises controlling 1208 theauxiliary PA to provide a signal that has a phase and amplitude inrelation to the output of the power amplifier of the transmitter suchthat the transmitter contribution to the signal at the input of thereceiver is suppressed. As indicated by the dotted arrow, the method isan ongoing process at operation of the transceiver.

The method can optionally include controlling 1203 impedances and/orfilters of the transceiver. For example, when a signal transmissionarrangement of the transceiver comprises a first impedance elementconnected between an output of the auxiliary power amplifier and aninput of the receiver, and a second impedance element connected betweenan output of the power amplifier of the transmitter and the input of thereceiver, wherein the first impedance element has controllable impedanceand the second impedance element has controllable impedance, as forexample demonstrated with reference to FIG. 2, 3 or 4, the method cancomprise controlling the impedances of the first and second impedanceelements.

Depending on the structure of the transceiver, the controlling of theauxiliary power amplifier can be made to, at its output, have a relationin phase to the output of the power amplifier of the transmitter and tohave an amplitude, at its output, having a relation to the output of thepower amplifier of the transmitter, and the first and second impedanceelements to have a corresponding relation of their impedances. Further,the controlling can comprise controlling the auxiliary power amplifierto have, at its output, opposite phase to the output of the poweramplifier of the transmitter and to have, at its output, equal amplitudeto the output of the power amplifier of the transmitter, and the firstand second impedance elements have equal impedances.

For a structure as for example the one depicted in FIG. 5, the methodcan further comprise controlling a controllable capacitance 521.

For a structure as for example the one depicted in FIG. 6 the method canfurther comprise controlling the filter 617.

For a structure as for example the one depicted in FIG. 7, the methodcan further comprise controlling the filter 717, e.g. by controlling theimpedance 734 and/or the capacitance 732. For a structure as for examplethe one depicted in FIG. 8, the similar applies.

For a structure as for example the one depicted in FIG. 9, the methodcan further comprise controlling the filter 921.

The controlling can be feedback controlling by measuring 1201 signalsand providing control based thereon. The controlling can for example befeedback controlling by measuring 1201 the output of the power amplifierof the transmitter and the output of the auxiliary power amplifierwherein the feedback controlling is based on the measurements. Thecontrolling can feedback controlling by measuring 1201 the transmittercontribution at the input of the receiver wherein the feedbackcontrolling is based on the measurement. The controlling can also be acombination of these.

For a structure including a controllable receiver impedance element atthe input of the receiver, the method can further comprise controllingthe impedance of the receiver impedance element such that a path towardsthe receiver of the signal transmission arrangement and the receiverimpedance element together have a resonance frequency equal to afrequency of a signal desired to be received by the receiver. Thereby,low loss from the antenna to the receiver can be kept.

The methods according to the present invention are suitable forimplementation with aid of processing means, such as computers and/orprocessors, especially for the case where the controlling of thetransceiver according to the embodiment described above is performed bysuch processing means. Therefore, there is provided computer programs,comprising instructions arranged to cause the processing means,processor, or computer to perform the steps of any of the methodsaccording to any of the embodiments described with reference to FIG. 12.The computer programs preferably comprises program code which is storedon a computer readable medium 1300, as illustrated in FIG. 13, which canbe loaded and executed by a processing means, processor, or computer1302 to cause it to perform the methods, respectively, according toembodiments of the present invention, preferably as any of theembodiments described with reference to FIG. 12. The computer 1302 andcomputer program product 1300 can be arranged to execute the programcode sequentially where actions of the any of the methods are performedstepwise. The processing means, processor, or computer 1302 ispreferably what normally is referred to as an embedded system. Thus, thedepicted computer readable medium 1300 and computer 1302 in FIG. 13should be construed to be for illustrative purposes only to provideunderstanding of the principle, and not to be construed as any directillustration of the elements.

FIG. 14 is a block diagram schematically illustrating a communicationdevice 1400 according to an embodiment. The communication device 1400,which can be a mobile terminal, a communication card e.g. in a laptop,controller of a machine or other processing device, or a network node,comprises a transceiver arrangement 1402 as any of those demonstratedabove, further signal processing means 1404, and one or more interfaces1406, e.g. electrical, optical, or user interfaces. The transceiverarrangement 1402 handles wireless communication with e.g. cellularcommunication network nodes, cellular terminals, point-to-pointcommunication nodes, etc., and optionally also other entities. Inputsand outputs from and to the wireless operations are provided to and fromthe further signal processing means 1404. The further signal processingmeans 1404 is enabled to interact through the one or more interfaces1406.

FIG. 15 is a block diagram schematically illustrating a transceiver 1500applying an approach for controlling auxiliary power amplifier output byapplying adjustments in the auxiliary power amplifier 1512. The samesignal as provided to the power amplifier 1508 of the main poweramplifier is then provided to the auxiliary power amplifier path.

FIG. 16 is a block diagram schematically illustrating a transceiver 1600applying an approach for controlling auxiliary power amplifier output byapplying adjustments in a circuit 1611 for adjusting phase and amplitudeinput to the auxiliary power amplifier 1612. The same signal as providedto the power amplifier 1608 of the main power amplifier is then providedto the circuit 1611 for adjusting phase and amplitude wherein theadjusted signal then is provided further in the auxiliary poweramplifier path.

FIG. 17 is a block diagram schematically illustrating a transceiver 1700applying an approach for controlling auxiliary power amplifier output byapplying adjustments in a baseband circuit 1701 connected to thetransceiver as demonstrated with reference to any of FIGS. 2 to 9.Different signals can then be provided to the power amplifier 1708 ofthe main power and the auxiliary power amplifier 1712 path. Theadjustment in the baseband circuit 1701 can be done either in digitaldomain or in analog domain.

In all of the approaches demonstrated with reference to FIGS. 15 to 17,the controller provides the control of the output of the auxiliary poweramplifier. Any of the approaches demonstrated with reference to FIGS. 15to 17 can be applied to any of the structures demonstrated withreference to FIGS. 2 to 9.

The invention has mainly been described above with reference to a fewembodiments. However, as is readily appreciated by a person skilled inthe art, other embodiments than the ones disclosed above are equallypossible within the scope of the invention, as defined by the appendedpatent claims.

1-51. (canceled)
 52. A transceiver suitable for frequency duplexdivision communication, the transceiver comprising: a transmitter, thetransmitter comprising a power amplifier; a receiver; an auxiliary poweramplifier configured to provide a controllable phase shift and gainoutput; a first filter arranged at an output of the power amplifier andconfigured to attenuate frequencies at a receiving frequency of thereceiver; a second filter at an output of the auxiliary power amplifierand configured to attenuate frequencies at a receiving frequency of thereceiver; a signal transmission arrangement configured to: transmitsignals provided from the transmitter through its power amplifier to aradio frequency (RF) connecting point via the second filter; receivesignals from the RF connecting point and provide the signals to thereceiver; and provide signals from the auxiliary amplifier towards aninput of the receiver; a controller configured to control the auxiliarypower amplifier output to provide a signal that has a phase andamplitude in relation to the output of the power amplifier of thetransmitter such that the transmitter contribution to the signal at theinput of the receiver is suppressed.
 53. The transceiver of claim 52,wherein: the receiving frequency of the receiver is lower than atransmitting frequency of the transmitter; the first filter is ahigh-pass filter or a band-pass filter; and the second filter is ahigh-pass filter or a band-pass filter.
 54. The transceiver of claim 53,wherein the band-pass filters of the first and second filters eachcomprises a capacitance and a first inductance coupled in parallel wherethe parallel coupling is coupled in series with a second inductance. 55.The transceiver of claim 54, wherein at least one of the capacitance andthe first and second inductances of each of the first and second filtersare controllable and are controlled by the controller.
 56. Thetransceiver of claim 52, wherein: the receiving frequency of thereceiver is higher than a transmitting frequency of the transmitter, thefirst filter is a low-pass filter or a band-pass filter; and the secondfilter is a low-pass filter or a band-pass filter.
 57. The transceiverof claim 56, wherein the band-pass filters of the first and secondfilters each comprises a first capacitance and an inductance coupled inparallel, where the parallel coupling is coupled in series with a secondcapacitance.
 58. The transceiver of claim 57, wherein at least one ofthe inductance and the first and second capacitances of each of thefirst and second filters are controllable and are controlled by thecontroller.
 59. The transceiver of claim 52, wherein the controller isconfigured to control an input to the auxiliary power amplifier suchthat the auxiliary power amplifier is enabled to provide thecontrollable phase shift and gain output.
 60. The transceiver of claim59, wherein the control of the input to the auxiliary power amplifier isa control of a baseband circuit connected to the transceiver.
 61. Thetransceiver of claim 52, wherein the controller is configured to controlthe auxiliary power amplifier such that the auxiliary power amplifier isenabled to provide the controllable phase shift and gain output.
 62. Thetransceiver of claim 52, wherein the signal transmission arrangementcomprises: a first impedance element connected between an output of theauxiliary power amplifier filter and an input of the receiver; and asecond impedance element connected between an output of the poweramplifier filter of the transmitter and the input of the receiverwherein the second impedance element also is connected between the RFconnecting point and the input of the receiver.
 63. The transceiver ofclaim 62, wherein: the first impedance element has controllableimpedance; the second impedance element has controllable impedance; andthe controller is configured to control also impedances of the firstimpedance element and the second impedance element.
 64. The transceiverof claim 63, wherein: the output of the auxiliary power amplifier iscontrolled to have a relation in phase to the output of the poweramplifier of the transmitter and to have an amplitude having a relationto the output of the power amplifier of the transmitter; and the firstand second impedance elements are controlled to have a correspondingrelation of their impedances.
 65. The transceiver of claim 64, wherein:the output of the auxiliary power amplifier is controlled to haveopposite phase to the output of the power amplifier of the transmitterand to have equal amplitude to the output of the power amplifier of thetransmitter; and the first and second impedance elements have equalimpedances.
 66. The transceiver of claim 62, wherein: the secondimpedance element comprises a first and a second impedance connected inseries; the controller is configured to provide its control by afeedback structure and measure at a point between the first and secondimpedances of the second impedance element and the output of theauxiliary power amplifier; wherein feedback is based on themeasurements.
 67. The transceiver of claim 62: further comprising aparallel resonance tank circuit including the first and second impedanceelements and a third impedance element connected between the output ofthe second filter of the auxiliary power amplifier and first filter ofthe power amplifier of the transmitter; wherein the parallel resonancetank is tuned to a frequency of a signal component received by thesignal transmission arrangement that is desired to be suppressed. 68.The transceiver of claim 62, wherein: the receiver further comprises areceiver impedance element at the input of the receiver, the receiverimpedance element having controllable impedance; the controller isconfigured to control the receiver impedance element such that thesecond impedance element and the receiver impedance element togetherhave a resonance frequency equal to a frequency of a signal desired tobe received by the receiver.
 69. The transceiver of claim 62, whereinthe first and second impedance elements comprise inductors.
 70. Thetransceiver of claim 62, wherein the first and second impedance elementscomprise capacitors.
 71. The transceiver of claim 52, wherein the signaltransmission arrangement comprises: a connection coupling the outputsignal from the first filter to the RF connecting point; a primarywinding coupling a signal from the RF connecting point to the receivervia a capacitance; and a secondary winding interacting with the primarywinding and coupled to the output of the second filter of the auxiliarypower amplifier such that the provision of the signals from theauxiliary power amplifier is enabled.
 72. The transceiver of claim 52,wherein: the signal transmission arrangement comprises a primary windingconnected to the RF connecting point and a secondary winding interactingwith the primary winding; the secondary winding is coupling a signalfrom the RF connecting point to the receiver; and wherein the primarywinding is coupled: to the output of the second filter of the auxiliarypower amplifier such that the provision of the signals from theauxiliary power amplifier is enabled; and to a third filter connected toa reference voltage such that current swing at the receiving frequencyis enabled in the primary winding.
 73. The transceiver of claim 52:wherein the signal transmission arrangement comprises a primary windingconnected to the RF connecting point, and a secondary windinginteracting with the primary winding, wherein the secondary winding iscoupling a signal from the RF connecting point to the receiver; whereinthe primary winding is coupled to a third filter connected to areference voltage such that current swing at the receiving frequency isenabled across the primary winding; wherein the third filter comprises afurther primary winding; wherein a further secondary winding interactingwith the further primary winding is coupled to the output of the secondfilter of the auxiliary power amplifier such that the provision of thesignals from the auxiliary power amplifier is enabled.
 74. Thetransceiver of claim 52: wherein the signal transmission arrangementcomprises a first primary winding connected to the RF connecting point,a second primary winding, and secondary winding interacting with thefirst and secondary primary windings; wherein the secondary winding iscoupling a signal from the RF connecting point to the receiver; whereinthe first primary winding is coupled to a third filter connected to areference voltage such that current swing at the receiving frequency isenabled in the first primary winding; wherein the second primary windingis coupled to the output of the second filter of the auxiliary poweramplifier such that the provision of the signals from the auxiliarypower amplifier is enabled.
 75. The transceiver of claim 52: wherein thesignal transmission arrangement comprises: a connection coupling theoutput signal from the first filter to the RF connecting point; a thirdfilter coupling a signal from the RF connecting point to the receiver;wherein the output of the second filter is connected directly to theinput of the receiver.
 76. The transceiver of claim 75, wherein: thereceiving frequency of the receiver is lower than a transmittingfrequency of the transmitter; and the third filter is a low-pass filteror a band-pass filter.
 77. The transceiver of claim 76, wherein theband-pass filter of third filter comprises a first capacitance and aninductance coupled in parallel, where the parallel coupling is coupledin series with a second capacitance.
 78. The transceiver of claim 77,wherein at least one of the inductance and the first and secondcapacitances of the third filter is controllable and is controlled bythe controller.
 79. The transceiver of claim 75, wherein: the receivingfrequency of the receiver is higher than a transmitting frequency of thetransmitter; and the third filter is a high-pass filter or a band-passfilter.
 80. The transceiver of claim 79, wherein the band-pass filter ofthird filter comprises a capacitance and a first inductance coupled inparallel, with the parallel coupling coupled in series with a secondinductance.
 81. The transceiver of claim 80, wherein at least one of thecapacitance and the first and second inductances of the third filter iscontrollable and is controlled by the controller.
 82. The transceiver ofclaim 52, wherein: the controller is configured to provide its controlby a feedback structure and measure the output of the power amplifier ofthe transmitter and the output of the auxiliary power amplifier;feedback is based on the measurements.
 83. The transceiver of claim 52,wherein: the controller is configured to provide its control by afeedback structure and measure the transmitter contribution at the inputof the receiver; feedback is based on the measurement.
 84. Acommunication device, capable of frequency division duplex communicationin a communication network, the communication device comprising: atransceiver; wherein the transceiver comprises: a transmitter, thetransmitter comprising a power amplifier; a receiver; an auxiliary poweramplifier configured to provide a controllable phase shift and gainoutput; a first filter arranged at an output of the power amplifier andconfigured to attenuate frequencies at a receiving frequency of thereceiver; a second filter at an output of the auxiliary power amplifierand configured to attenuate frequencies at a receiving frequency of thereceiver; a signal transmission arrangement configured to: transmitsignals provided from the transmitter through its power amplifier to aradio frequency (RF) connecting point via the second filter; receivesignals from the RF connecting point and provide the signals to thereceiver; and provide signals from the auxiliary amplifier towards aninput of the receiver; a controller configured to control the auxiliarypower amplifier output to provide a signal that has a phase andamplitude in relation to the output of the power amplifier of thetransmitter such that the transmitter contribution to the signal at theinput of the receiver is suppressed.